Point of presence management in request routing

ABSTRACT

A system and method for the management of client computing device DNS queries and subsequent resource requests within a content delivery network service provider domain are provided. The management of the DNS queries can include the selection of computing devices corresponding to various Point of Presence locations for processing DNS queries. Additionally, the management of the content requests can include the selection of computing devices corresponding to resource cache components corresponding to various Point of Presence locations for providing requested content. The selection of the computing devices can incorporate logic related to geographic criteria, performance threshold criteria, testing criteria, and the like.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No. 12/892,822 now U.S. Pat. No. 8,468,247, entitled “POINT OF PRESENCE MANAGEMENT IN REQUEST ROUTING” and filed Sep. 28, 2010, and is related to U.S. patent application Ser. No. 13/620,976, now U.S. Pat. No. 8,676,918, entitled “POINT OF PRESENCE MANAGEMENT IN REQUEST ROUTING” and filed Sep. 15, 2012, the disclosures of which are incorporated herein by reference.

BACKGROUND

Generally described, computing devices and communication networks can be utilized to exchange information. In a common application, a computing device can request content from another computing device via a communication network. For example, a user at a personal computing device can utilize a software browser application to request a Web page from a server computing device via the Internet. In such embodiments, the user computing device can be referred to as a client computing device and the server computing device can be referred to as a content provider.

Content providers are generally motivated to provide requested content to client computing devices, often with consideration of efficient transmission of the requested content to the client computing device and/or consideration of a cost associated with the transmission of the content. For larger scale implementations, a content provider may receive content requests from a high volume of client computing devices, which can place a strain on the content provider's computing resources. Additionally, the content requested by the client computing devices may have a number of components, which can further place additional strain on the content provider's computing resources.

With reference to an illustrative example, a requested Web page, or original content, may be associated with a number of additional resources, such as images or videos, that are to be displayed with the Web page. In one specific embodiment, the additional resources of the Web page are identified by a number of embedded resource identifiers, such as uniform resource locators (“URLs”). In turn, software on the client computing devices typically processes embedded resource identifiers to generate requests for the content. Often, the resource identifiers associated with the embedded resources reference a computing device associated with the content provider such that the client computing device would transmit the request(s) for the additional resources to the referenced content provider computing device. Accordingly, in order to satisfy a content request, the content provider would provide client computing devices data associated with the Web page as well as the data associated with the embedded resources (e.g., embedded resource identifiers).

Some content providers attempt to facilitate the delivery of requested content, such as Web pages and/or resources identified in Web pages, through the utilization of a content delivery network (“CDN”) service provider. A CDN service provider typically maintains a number of computing devices in a communication network that can maintain content from various content providers. In turn, content providers can instruct, or otherwise suggest to, client computing devices to request some, or all, of the content provider's content from the CDN service provider's computing devices.

As with content providers, CDN service providers are also generally motivated to provide requested content to client computing devices, often with consideration of efficient transmission of the requested content to the client computing device and/or consideration of a cost associated with the transmission of the content. Accordingly, CDN service providers often consider factors such as latency of delivery of requested content in order to meet service level agreements or to generally improve the quality of delivery service. The consideration of such factors can be applied with regard to decisions by a CDN service provider as to which of the several available computing devices is best suited to process client computing device requests for content.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a block diagram illustrative of a content delivery environment including a number of client computing devices, a content provider, and a content delivery network service provider;

FIG. 2 is a block diagram of the content delivery environment of FIG. 1 illustrating the registration of a content provider with a content delivery service provider;

FIG. 3 is a block diagram of the content delivery environment of FIG. 1 illustrating the generation and processing of a content request from a client computing device to a content provider;

FIG. 4 is a block diagram of the content delivery environment of FIG. 1 illustrating the generation and processing of a DNS query corresponding to an embedded resource from a client computing device to a content delivery network service provider;

FIG. 5 is a block diagram of the content delivery environment of FIG. 1 illustrating the forwarding of a DNS query to an alternative DNS server component;

FIG. 6 is a block diagram of the content delivery environment of FIG. 1 illustrating the generation and processing of a DNS query with alternative resource identifiers;

FIG. 7 is a block diagram of the content delivery environment of FIG. 1 illustrating the generation and processing of embedded resource requests from a client computing device to a content delivery network service provider;

FIG. 8 is a flow diagram illustrative of a request routing routine implemented by a content delivery network service provider utilization of a series of alternative resource identifiers;

FIG. 9 is a flow diagram illustrative of a Point of Presence selection sub-routine implemented by a content delivery network service provider;

FIG. 10 is a flow diagram illustrative of a Point of Presence selection sub-routine implemented by a content delivery network service provider; and

FIGS. 11-13 are block diagrams illustrative of the approximation of geographic distance of various nodes of a communication network for use in the selection of a Point of Presence location.

DETAILED DESCRIPTION

Generally described, aspects of the present disclosure are directed to routing of DNS queries from client computing devices. The DNS queries correspond to content requests provided by a network resource, such as content delivery network (“CDN”) service providers. Specifically, aspects of the disclosure will be described with regard to the management of client computing device DNS queries and subsequent resource requests within a content delivery network service provider domain. Illustratively, the management of the DNS queries can include the selection of computing devices corresponding to various Point of Presence (“POP”) locations for processing DNS queries. Additionally, the management of the content requests can include the selection of computing devices corresponding to resource cache components corresponding to various POP locations for providing requested content. The selection of the computing devices can incorporate logic related to geographic criteria, performance threshold criteria, testing criteria, and the like. Although various aspects of the disclosure will be described with regard to illustrative examples and embodiments, one skilled in the art will appreciate that the disclosed embodiments and examples should not be construed as limiting.

FIG. 1 is a block diagram illustrative of content delivery environment 100 for the management and processing of content requests. As illustrated in FIG. 1, the content delivery environment 100 includes a number of client computing devices 102 (generally referred to as clients) for requesting content from a content provider, a CDN service provider, or other service provider. In an illustrative embodiment, the client computing devices 102 can correspond to a wide variety of computing devices, including personal computing devices, laptop computing devices, hand-held computing devices, terminal computing devices, mobile devices, wireless devices, various electronic devices and appliances and the like. In an illustrative embodiment, the client computing devices 102 include necessary hardware and software components for establishing communications over a communication network 108, such as a wide area network or local area network. For example, the client computing devices 102 may be equipped with networking equipment and browser software applications that facilitate communications via the Internet or an intranet.

Although not illustrated in FIG. 1, each client computing device 102 can utilize some type of local DNS resolver component, such as a DNS Name server, that generates the DNS queries attributed to the client computing device 102. In one embodiment, the local DNS resolver component may be provided by an enterprise network to which the client computing device 102 belongs. In another embodiment, the local DNS resolver component may be provided by an Internet Service Provider (“ISP”) that provides the communication network connection to the client computing device 102. However, for purposes of the present disclosure, communications facilitated through a network component, such as a DNS resolver component, will be illustrated as transmitted directly from the client computing devices 102.

The content delivery environment 100 can also include a content provider 104 in communication with the one or more client computing devices 102 via the communication network 108. The content provider 104 illustrated in FIG. 1 corresponds to a logical association of one or more computing devices associated with a content provider. Specifically, the content provider 104 can include a web server component 110 corresponding to one or more server computing devices for obtaining and processing requests for content (such as Web pages) from the client computing devices 102. The content provider 104 can further include an origin server component 112 and associated storage component 114 corresponding to one or more computing devices for obtaining and processing requests for network resources from the CDN service provider. One skilled in the relevant art will appreciate that the content provider 104 can be associated with various additional computing resources, such as additional computing devices for administration of content and resources, DNS name servers, and the like. For example, although not illustrated in FIG. 1, the content provider 104 can be associated with one or more DNS name server components that would be authoritative to resolve client computing device DNS queries corresponding to a domain of the content provider.

With continued reference to FIG. 1, the content delivery environment 100 can further include a CDN service provider 106 in communication with the one or more client computing devices 102 and the content provider 104 via the communication network 108. The CDN service provider 106 illustrated in FIG. 1 corresponds to a logical association of one or more computing devices associated with a CDN service provider. Specifically, the CDN service provider 106 can include a number of POP locations 116, 122, 128 that correspond to nodes on the communication network 108. Each POP 116, 122, 128 includes a DNS component 118, 124, 130 made up of a number of DNS server computing devices for resolving DNS queries from the client computing devices 102. Each POP 116, 122, 128 also includes a resource cache component 120, 126, 132 made up of a number of cache server computing devices for storing resources from content providers and transmitting various requested resources to various client computers. The DNS components 118, 124 and 130 and the resource cache components 120, 126, 132 may further include additional software and/or hardware components that facilitate communications including, but not limited to, load balancing or load sharing software/hardware components.

In an illustrative embodiment, the DNS component 118, 124, 130 and resource cache component 120, 126, 132 are considered to be logically grouped, regardless of whether the components, or portions of the components, are physically separate. Additionally, although the POPs 116, 122, 128 are illustrated in FIG. 1 as logically associated with the CDN service provider 106, the POPs will be geographically distributed throughout the communication network 108 in a manner to best serve various demographics of client computing devices 102. Additionally, one skilled in the relevant art will appreciate that the CDN service provider 106 can be associated with various additional computing resources, such as additional computing devices for administration of content and resources, and the like.

With reference now to FIGS. 2-7, the interaction between various components of the content delivery environment 100 of FIG. 1 will be illustrated. For purposes of the example, however, the illustration has been simplified such that many of the components utilized to facilitate communications are not shown. One skilled in the relevant art will appreciate that such components can be utilized and that additional interactions would accordingly occur without departing from the spirit and scope of the present disclosure.

With reference to FIG. 2, an illustrative interaction for registration of a content provider 104 with the CDN service provider 106 will be described. As illustrated in FIG. 2, the CDN content registration process begins with registration of the content provider 104 with the CDN service provider 106. In an illustrative embodiment, the content provider 104 utilizes a registration application program interface (“API”) to register with the CDN service provider 106 such that the CDN service provider 106 can provide content on behalf of the content provider 104. The registration API includes the identification of the origin server 112 of the content provider 104 that will provide requested resources to the CDN service provider 106.

One skilled in the relevant art will appreciate that upon identification of appropriate origin servers 112, the content provider 104 can begin to direct requests for content from client computing devices 102 to the CDN service provider 106. Specifically, in accordance with DNS routing principles, a client computing device request corresponding to a resource identifier would eventually be directed toward a POP 116, 122, 128 associated with the CDN service provider 106. In the event that the resource cache component 120, 126, 132 of a selected POP does not have a copy of a resource requested by a client computing device 102, the resource cache component will request the resource from the origin server 112 previously registered by the content provider 104.

With continued reference to FIG. 2, upon receiving the registration API, the CDN service provider 106 obtains and processes the registration information. In an illustrative embodiment, the CDN service provider 106 can then generate additional information that will be used by the client computing devices 102 as part of the content requests. The additional information can include, without limitation, client identifiers, such as client identification codes, content provider identifiers, such as content provider identification codes, executable code for processing resource identifiers, such as script-based instructions, and the like. One skilled in the relevant art will appreciate that various types of additional information may be generated by the CDN service provider 106 and that the additional information may be embodied in any one of a variety of formats.

Illustratively, the CDN service provider 106 returns an identification of applicable domains for the CDN service provider (unless it has been previously provided) and any additional information to the content provider 104. In turn, the content provider 104 can then process the stored content with content provider specific information. In one example, as illustrated in FIG. 2, the content provider 104 translates resource identifiers originally directed toward a domain of the origin server 112 to a domain corresponding to the CDN service provider. The translated URLs are embedded into requested content in a manner such that DNS queries for the translated URLs will resolve to a DNS server corresponding to the CDN service provider 106 and not a DNS server corresponding to the content provider 104. Although the translation process is illustrated in FIG. 2, in some embodiments, the translation process may be omitted in a manner described in greater detail below.

Generally, the identification of the resources originally directed to the content provider 104 will be in the form of a resource identifier that can be processed by the client computing device 102, such as through a browser software application. In an illustrative embodiment, the resource identifiers can be in the form of a uniform resource locator (“URL”). Because the resource identifiers are included in the requested content directed to the content provider, the resource identifiers can be referred to generally as the “content provider URL.” For purposes of an illustrative example, the content provider URL can identify a domain of the content provider 104 (e.g., contentprovider.com), a name of the resource to be requested (e.g., “resource.xxx”) and a path where the resource will be found (e.g., “path”). In this illustrative example, the content provider URL has the form of:

-   -   http://www.contentprovider.com/path/resource.xxx

During an illustrative translation process, the content provider URL is modified such that requests for the resources associated with the translated URLs resolve to a POP associated with the CDN service provider 106. In one embodiment, the translated URL identifies the domain of the CDN service provider 106 (e.g., “cdnprovider.com”), the same name of the resource to be requested (e.g., “resource.xxx”) and the same path where the resource will be found (e.g., “path”). Additionally, the translated URL can include additional processing information (e.g., “additional information”). The translated URL would have the form of:

-   -   http://additional_information.cdnprovider.com/path/resources.xxx

In another embodiment, the information associated with the CDN service provider 106 is included in the modified URL, such as through prepending or other techniques, such that the translated URL can maintain all of the information associated with the original URL. In this embodiment, the translated URL would have the form of:

-   -   http://additional_information.cdnprovider.com/www.contentprovider.com/path/resource.xxx

With reference now to FIG. 3, after completion of the registration and translation processes illustrated in FIG. 2, a client computing device 102 subsequently generates a content request that is received and processed by the content provider 104, such as through the Web server 110. In accordance with an illustrative embodiment, the request for content can be in accordance with common network protocols, such as the hypertext transfer protocol (“HTTP”). Upon receipt of the content request, the content provider 104 identifies the appropriate responsive content. In an illustrative embodiment, the requested content can correspond to a Web page that is displayed on the client computing device 102 via the processing of information, such as hypertext markup language (“HTML”), extensible markup language (“XML”), and the like. The requested content can also include a number of embedded resource identifiers, described above, that correspond to resource objects that should be obtained by the client computing device 102 as part of the processing of the requested content. The embedded resource identifiers can be generally referred to as original resource identifiers or original URLs regardless of whether they have been translated in the manner described above.

Upon receipt of the requested content, the client computing device 102, such as through a browser software application, begins processing any of the markup code included in the content and attempts to acquire the resources identified by the embedded resource identifiers. Accordingly, the first step in acquiring the content corresponds to the issuance, by the client computing device 102 (through its local DNS resolver), a DNS query for the original URL resource identifier that results in the identification of a DNS server authoritative to the “.” and the “com” portions of the translated URL. After resolving the “.” and “com” portions of the embedded URL, the client computing device 102 then issues a DNS query for the resource URL that results in the identification of a DNS server authoritative to the “.cdnprovider” portion of the embedded URL. The issuance of DNS queries corresponding to the “.” and the “com” portions of a URL are well known and have not been illustrated.

With reference now to FIG. 4, in an illustrative embodiment, the successful resolution of the “cdnprovider” portion or “contentprovider” portion of the original URL identifies a network address, such as an IP address, of a DNS server associated with the CDN service provider 106. In one embodiment, the IP address is a specific network address unique to a DNS server component of a POP. In another embodiment, the IP address can be shared by one or more POPs. In this embodiment, a further DNS query to the shared IP address utilizes a one-to-many network routing schema, such as anycast, such that a specific POP will receive the request as a function of network topology. For example, in an anycast implementation, a DNS query issued by a client computing device 102 to a shared IP address will arrive at a DNS server component logically having the shortest network topology distance, often referred to as network hops, from the client computing device. The network topology distance does not necessarily correspond to geographic distance. However, in some embodiments, the network topology distance can be inferred to be the shortest network distance between a client computing device 102 and a POP.

With continued reference to FIG. 4, in either of the above identified embodiments (or any other embodiment), a specific DNS server in the DNS component 118 of a POP 116 receives the DNS query transmitted by the client computing device 102 and corresponding to the original URL of the embedded resource identifier. Once one of the DNS servers in the DNS component 118 receives the request, the specific DNS server attempts to resolve the request. Generally, a specific DNS server can resolve the DNS query by identifying an IP address of a cache server component that will process the request for the requested resource. As described above, a selected resource cache component can process the request by either providing the requested resource if it is available or attempting to obtain the requested resource from another source, such as a peer cache server computing device or the origin server 112 of the content provider 104.

In one embodiment, the DNS server resolves the DNS query by providing the IP address of a default resource cache component associated with the receiving DNS server, such as the resource cache component located at the same POP. In this embodiment, the CDN service provider 106 illustratively has utilized logic in the selection of the receiving DNS server component. In another embodiment, the receiving DNS server component can utilize additional or alternative logic in selecting resource cache components associated with various POPs provided by the CDN service provider 106. In this embodiment, the example routines for the selection of alternative DNS servers illustrated in FIGS. 8-10 could be applied in the selection of a resource cache component.

Referring now to FIGS. 5 and 6, if the receiving DNS server is not capable of resolving the DNS query (e.g., the receiving DNS server is not authoritative) or if CDN service provider 106 determines that another DNS server at another POP should resolve the DNS server, the specific receiving DNS server will cause the DNS query to be received by another DNS server. Example routines for the selection of alternative DNS query will be described with regard to FIGS. 8-10. As will be explained in greater detail below, the routing of a received DNS query to an alternative DNS server component can be achieved in various manners and can be implemented independently of any additional logic in the identification of one or more resource cache components (e.g., resolution of the DNS query) or in conjunction with additional or alternative logic utilized in the identification of one or more resource cache components.

With reference to FIG. 5, in one alternative embodiment for causing the receipt of a DNS query by another DNS server, the receiving DNS server can process additional information included in an original URL DNS query and utilize logic to select an alternative DNS server provided by the CDN service provider 106 or another service provider. With reference to the previous illustrative original URL format, the receiving DNS server can parse the “additional information” included in the URL corresponding to the DNS query and apply various request routing criteria to identify one or more DNS server best suited to attempt to resolve the DNS query. For example, the additional information included in the URL can identify service plan information, geographic identifiers, account identifiers or other information utilized by the receiving DNS server to select an appropriate alternative DNS server. Example routines for the selection of alternative DNS servers will be discussed in greater detail below. As illustrated in FIG. 5, the receiving DNS server, such as a specific DNS server in the DNS component 118 of a POP 116, would forward the received DNS query to the DNS component 124 of POP 122. In this embodiment, the forwarding of the DNS query to an alternative POP may be achieved without additional interaction between the receiving DNS component 118 and the requesting client computing device.

With reference now to FIG. 6, in another alternative embodiment for causing the receipt of a DNS query by another DNS server, the CDN service provider 106 can maintain sets of various alternative resource identifiers that cause the client computing device 102 to transmit one or more subsequent DNS queries. The alternative resource identifiers can be provided by the CDN service provider 106 to the client computing device 102 such that a subsequent DNS query on the alternative resource identifier will resolve to a different DNS server component within the CDN service provider's network. In an illustrative embodiment, the alternative resource identifiers are in the form of one or more canonical name (“CNAME”) records. In one embodiment, each CNAME record identifies a domain of the CDN service provider 106 (e.g., “cdnprovider.com” or “cdnprovider-1.com”). As will be explained in greater detail below, the domain in the CNAME does not need to be the same domain found in original URL or in a previous CNAME record. Additionally, each CNAME record includes additional information, such as request routing information, (e.g., “request routing information”). An illustrative CNAME record can have the form of:

-   -   CNAME request_routing_information.cdnprovider.com

In accordance with an illustrative embodiment utilizing CNAMES, the DNS server maintains a data store that defines CNAME records for various original URLs. If a DNS query corresponding to a particular original URL matches an entry in the data store, the DNS server component 118 returns a CNAME record as defined in the data store. In an illustrative embodiment, the data store can include multiple CNAME records corresponding to a particular original URL. The multiple CNAME records would define a set of potential candidates that can be returned to the client computing device. In such an embodiment, the DNS server component 118, either directly or via a network-based service, can implement additional logic in selecting an appropriate CNAME from a set of possible of CNAMEs. In an illustrative embodiment, each DNS server component 118, 124, 130 maintains the same data stores that define CNAME records, which can be managed centrally by the CDN service provider 106. Alternatively, each DNS server component 118, 124, 130 can have a POP specific data stores that define CNAME records, which can be managed centrally by the CDN service provider 106 or locally at the POP 116, 122, 128.

The returned CNAME can also include request routing information that is different from or in addition to the information provided in URL/CNAME of the current DNS query. For example, if the CNAME selection is based on regional plan, a specific regional plan can be identified in the “request_routing_information” portion of the specific CNAME record. A similar approach could be taken to identify service level plans and file management by including a specific identifier in the “request_routing_information” portion of the CNAME record. In another embodiment, request routing information can be found in the identification of a CDN service provider 106 domain different from the domain found in the current URL/CNAME. For example, if the CNAME is based on regional plan, a specific regional plan domain (e.g., “cdnprovider-region1.com”) could be used in the domain name portion of the specific CNAME record. Any additional request routing information can be prepended to the existing request routing information in the current URL/CNAME such that the previous request routing information would not be lost (e.g., CNAME serviceplan.regionalplan.cdnprovider.com). One skilled in the relevant art will appreciate that additional or alternative techniques and/or combination of techniques may be used to include the additional request routing information in the CNAME record that is selected by the DNS server component 118.

One skilled in the relevant art will appreciate that DNS server component 118 may select (or otherwise obtain) a CNAME record that is intended resolve to a more appropriate DNS server of the CDN service provider 106. It may be possible, however, that the same DNS server would also be authoritative for the subsequent DNS query for the CNAME to be provided to the client computing device. In such an embodiment, the DNS server, such as DNS server component 118, may choose to resolve the future DNS query in advance.

With continued reference to FIG. 6, upon receipt of the CNAME from the DNS server component 118, the client computing device 102 generates a subsequent DNS query corresponding to the CNAME. As previously discussed with regard to FIG. 4, the DNS query process could first start with DNS queries for the “.” and “com” portions, followed by a query for the “cdnprovider” portion of the CNAME. To the extent, however, that the results of a previous DNS queries can be cached (and remain valid), the client computing device 102 can utilize the cached information and does not need to repeat the entire process. However, at some point, depending on whether the CNAME provided by DNS server component 118 and the previous URL/CNAME share common CDN service provider domains, the DNS query resolves to a different POP provided by the CDN service provider 106. As illustrated in FIG. 6, the DNS server component 124 of POP 122 is now authoritative based on the different information in the current CNAME previously provided by the DNS server component 118. As previously described, the DNS server component 124 can then determine whether to resolve the DNS query on the CNAME with an IP address of a cache component that will process the content request or whether to provide another alternative resource identifier selected in the manner described above.

In an illustrative embodiment, the receiving DNS server components, such as DNS server component 130, can utilize a variety of information in selecting a resource cache component. In one example, the DNS server component can default to a selection of a resource cache component of the same POP. In another example, the DNS server components can select a resource cache component based on various load balancing or load sharing algorithms. Still further, the DNS server components can utilize network performance metrics or measurements to assign specific resource cache components. The IP address selected by a DNS server component may correspond to a specific caching server in the resource cache. Alternatively, the IP address can correspond to a hardware/software selection component (such as a load balancer).

With reference now to FIG. 7, in an illustrative example, assuming in the various embodiments described with regard to FIGS. 4, 5 and 6 that a receiving DNS server component has resolved a DNS query and identified the IP address of a resource cache component for providing the requested resource, upon receipt of the IP address for the resource cache component 132, the client computing device 102 transmits requests for the requested content to the resource cache component 132. The resource cache component 132 processes the request in a manner described above and the requested content is transmitted to the client computing device 102.

With reference now to FIG. 8, a request routine 800 implemented by the CDN service provider 106 will be described. One skilled in the relevant art will appreciate that actions/steps outlined for routine 800 may be implemented by one or many computing devices/components that are associated with the CDN service provider 106. Accordingly, routine 800 has been logically associated as being performed by the CDN service provider 106.

At block 802, one of the DNS server components 118, 124, 130 receives a DNS query corresponding to resource identifier. As previously discussed, the resource identifier can be a URL that has been embedded in content requested by the client computing device 102 and previously provided by the content provider 104. Alternatively, the resource identifier can also correspond to a CNAME provided by a content provider DNS server in response to a DNS query previously received from the client computing device 102. At decision block 804, a test is conducted to determine whether the current DNS server is authoritative to resolve the DNS query. In an illustrative embodiment, the DNS server can determine whether it is authoritative to resolve the DNS query if there are no CNAME records corresponding to the received resource identifier. In another embodiment, the DNS server can parse any additional information included in the URL corresponding to the DNS query and utilize the additional information to determine whether the receiving DNS server component is authoritative. For example, the additional information in the URL may include information, such as an identifier, that identifies the authoritative DNS server. Alternative or additional methodologies may also be practiced to determine whether the DNS server is authoritative.

If at decision block 804 the DNS server is not authoritative, at block 806, the DNS server component selects an alternative DNS server. As described above, in one embodiment, the receiving DNS server can select an alternative DNS server by utilizing an alternative resource identifier, such as a CNAME. In this embodiment, the receiving DNS server component can utilize a data store to identify an appropriate CNAME as a function of the current DNS query. Additionally, the DNS server component can also implement additional logical processing to select from a set of potential CNAMEs. In another embodiment, the receiving DNS server can forward the DNS query via the communication network to another DNS server component. Two example sub-routines for selection of the alternative DNS server will be described with regard to FIGS. 9 and 10. The routine 800 returns to block 802 where another DNS server component of the CDN service provider 106 receives the forwarded DNS query or a subsequent DNS query corresponding to a returned CNAME.

With reference again to block 804, if the receiving DNS server is authoritative (including a determination that the same DNS server will be authoritative for subsequent DNS queries), then at decision block 808, the receiving DNS server component determines whether any alternative DNS server should be selected.

In one embodiment, a receiving DNS server component may be authoritative because it can resolve the DNS query. However, the CDN service provider 106 may wish to have another authoritative server resolve the request. For example, the CDN service provider 106 may wish to balance the request requests among several DNS servers. In another example, the CDN service provider 106 may wish to test the performance of the DNS server component associated with other POPs in the CDN service providers domain. If the DNS server component is determined to select an alternative server, at block 810, the receiving DNS server selects an alternative DNS servers. As described above, in one embodiment, the receiving DNS server can select an alternative DNS server by utilizing an alternative resource identifier, such as a CNAME. In this embodiment, the receiving DNS server component can utilize a data store to identify an appropriate CNAME as a function of the current DNS query. Additionally, the DNS server component can also implement additional logical processing to select from a set of potential CNAMEs. In another embodiment, the receiving DNS server can forward the DNS query via the communication network to another DNS server component. Two example sub-routines for selection of the alternative DNS server will be described with regard to FIGS. 9 and 10. The routine 800 returns to block 802 where another DNS server component of the CDN service provider 106 receives the forwarded DNS query or a subsequent DNS query corresponding to a returned CNAME.

Referring again to decision block 808, if the receiving DNS server does not select an alternative server, the current DNS server resolves the DNS query by returning the IP address of cache server component. In a non-limiting manner, a number of methodologies for selecting an appropriate resource cache component have been previously discussed. For example, the receiving DNS server can implement the logic described in selecting the alternative DNS servers in FIGS. 9 and 10 to select a resource cache component. In another example, the receiving DNS server can select a default resource cache component, such as the resource cache component associated with the POP of the receiving DNS server. Additionally, as described above, the IP address may correspond to a specific cache server of a resource cache component or generally to a group of cache servers

Referring now to FIG. 9, a flow diagram illustrative of a Point of Presence selection sub-routine 900 based on a minimum performance threshold and implemented by the CDN service provider 106 will be described. One skilled in the relevant art will appreciate that actions/steps outlined for sub-routine 900 may be implemented by one or many computing devices/components that are associated with the CDN service provider 106. Accordingly, sub-routine 900 has been logically associated as being performed by the CDN service provider 106. Additionally, as described above, although sub-routine 900 will be described with regard to the selection of alternative DNS server components, sub-routine 900 may be implemented by a DNS server in the selection of resource cache components in resolving a DNS query.

At block 902, the DNS server obtains performance measurement information for a set of target POPs in the CDN service provider domain. In an illustrative embodiment, the set of target POPs can correspond to all the POPs within a CDN service provider 106 domain or a subset of POPs identified by other criteria, such as service level plans, geographic limitations, and the like. Illustratively, the performance measurement information corresponds to at least one value or category related to the delivery of resources. In one embodiment, the performance measurement information can correspond to values related to latency measurement information for providing resources. The latency information can be associated with the requesting client computing device 102, such as latency information from previous interactions with the specific client computing device. The latency information can also be associated with groupings of client computing devices 102, such as by ISP, geographic location, enterprise networks, DNS resolver components, and the like. Additionally, the latency information may be determined based on absolute latency measurements or relative latency measurements.

In another embodiment, the performance measurement information can correspond to categories, or levels, of performance as determined by the CDN service provider 106, ISPs, client computing devices 102 or other entity. For example, the performance measurement information can correspond to a classification of a POP according to a category (e.g., “gold” or “silver”) based on historical information. The category information may be measured in terms of absolute performance or relative performance according to other POPs. Still further, the category information may also be organized in accordance with other criteria, such as geographic organizational criteria, network affiliation organizational criteria, organization affiliation organizational criteria, and the like. One skilled in the relevant art will appreciate that additional or alternative performance measurement information may also be utilized or combined.

At block 904, the DNS server obtains minimum performance thresholds for selecting a POP. The performance threshold or set of performance thresholds will correspond to the performance information obtained in block 902. The performance threshold information may be maintained centrally by the CDN service provider 106 or managed individually at each POP (or by a set of POPs). At block 906, the sub-routine 900 proceeds to a loop by selecting the next POP in the set of POPs available to process the DNS query. At decision block 908, a test is conducted to determine whether the performance information associated with the currently selected POP is above the performance threshold. If so, the POP is added to a set of POPs available for selection at block 910.

If at decision block 908, the performance measurement information is not above the performance threshold, or once a POP has been added to the set of POPs available for selection, at decision block 912, a test is conducted to determine whether there are additional POPs in the original set of POPs. If so, the sub-routine 900 returns to block 906 for processing of the performance measurement information for the next POP in the original set of POPs. Alternatively, if no additional POPs remain in the original set of POPs, the sub-routine 900 returns with the selection of POP from the set of available POPs. In one embodiment, the POP selection can be based on a relative comparison of performance measurement information (e.g., the POP associated with the lowest latency). In another embodiment, the POP selection can be based on random selection or a weighted selection based on performance measurement information. In still another embodiment, additional criteria, such as geographic criteria, cost criteria, etc. may be utilized to select a POP from the set of available POPs.

Referring now to FIG. 10, a flow diagram illustrative of a Point of Presence selection sub-routine 1000 based on approximated geographic distance and implemented by the CDN service provider 106 will be described. One skilled in the relevant art will appreciate that actions/steps outlined for sub-routine 1000 may be implemented by one or many computing devices/components that are associated with the CDN service provider 106. Accordingly, sub-routine 1000 has been logically associated as being performed by the CDN service provider 106. Additionally, as described above, although sub-routine 1000 will be described with regard to the selection of alternative DNS server components, sub-routine 1000 may be implemented by a DNS server in the selection of resource cache components in resolving a DNS query.

At block 1002, the DNS server obtains performance measurement information for a set of target POPs in the CDN service provider domain. In an illustrative embodiment, the set of target POPs can correspond to all the POPs within a CDN service provider 106 domain or a subset of POPs identified by other criteria, such as service level plans, geographic limitations, and the like. In one embodiment, the performance measurement information can correspond to values related to latency measurement information for providing resources. The latency information can be associated with the requesting client computing device 102, such as latency information from previous interactions with the specific client computing device. The latency information can also be associated with groupings of client computing devices 102, such as by ISP, geographic location, enterprise networks, DNS resolver components, and the like. One skilled in the relevant art will appreciate that additional or alternative performance measurement information may also be utilized or combined.

At block 1004, the sub-routine 1000 proceeds to a loop by selecting the next POP in the set of POPs available to process the DNS query. At block 1006, the DNS server determines a maximum distance between the requesting client computing device (or other starting position) and the POP. In an illustrative embodiment, the maximum distance between a reference node and the POP corresponds to the product of the latency information for the reference node and the maximum speed for packet delivery. Illustratively, the reference node can correspond to a variety of network nodes or other identifiable components including, but not limited to, the client computing device 102, DNS servers, DNS resolvers, network storage location, network computing device locations, mobile terminals, mobile infrastructure equipment, and the like.

With reference to FIG. 11, assume that a portion of the communication network 108 includes a number of nodes 1102-1128. Assume that the client computing device 102 corresponds to node 1102 and that CDN service provider's domain includes POPs corresponding to nodes 1116, 1118 and 1124. As also illustrated in FIG. 11, the actual path of communications between node 1102 and 1116, path 1130, corresponds to network intermediate communications through nodes 1110, 1112 and 1114. Likewise, the actual path of communications between node 1102 and 1118, path 1132, corresponds to network intermediate communications through node 1110. Still further, the actual path of communications between node 1102 and 1124, path 1134, corresponds to network intermediate communications through nodes 1108, 1120, and 1122. With reference now to FIG. 12, it can be assumed that the maximum distance between node 1102 and nodes 1116, 1118 and 1124, respectively paths 1130, 1132, and 1134 is a straight line between the two nodes the distance of which is the product of the latency in communications and the maximum speed of communications (e.g., the speed of light). In this embodiment, the latency caused by the intermediate nodes in the actual network paths is ignored for purposes of determining the maximum geographic distance between the starting nodes and the POPs.

At decision block 1008, a test is conducted to determine whether the maximum distance associated with the currently selected POP is above the maximum geographic threshold allowed for a POP. If not, the POP is added to a set of POPs available for selection at block 1010. FIG. 13 illustrates the three calculated maximum distances for paths 1130, 1132, 1134 between node 1102 and nodes 1116, 1118 and 1124, respectively. Additionally, the maximum geographic threshold is illustrated as a circle 1136 having a radius corresponding to the calculated maximum geographic threshold from the central node in any direction. As illustrated in FIG. 13, the calculated maximum geographic distance for path 1130 and 1132 is within the maximum geographic threshold 1136, while the calculated maximum geographic distance for path 1134 is above the maximum geographic threshold 1136. One skilled in the relevant art will appreciate that alternative geographic shapes or multiple geographic maximums may be implemented.

If at decision block 1008, the calculated geographic distance is above the maximum distance, or once a POP has been added to the set of POPs available for selection, at decision block 1012, a test is conducted to determine whether there are additional POPs in the original set of POPs. If so, the sub-routine 1000 returns to block 1004 for processing of the performance measurement information for the next POP in the original set of POPs. Alternatively, if no additional POPs remain in the original set of POPs, the sub-routine 1000 returns with the selection of POP from the set of available POPs. In one embodiment, the POP selection can be based on a relative comparison of performance measurement information (e.g., the POP associated with the lowest latency). In another embodiment, the POP selection can be based on random selection or a weighted selection based on performance measurement information. In still another embodiment, additional criteria, such as geographic criteria, cost criteria, etc. may be utilized to select a POP from the set of available POPs.

While illustrative embodiments have been disclosed and discussed, one skilled in the relevant art will appreciate that additional or alternative embodiments may be implemented within the spirit and scope of the present invention. Additionally, although many embodiments have been indicated as illustrative, one skilled in the relevant art will appreciate that the illustrative embodiments do not need to be combined or implemented together. As such, some illustrative embodiments do not need to be utilized or implemented in accordance with scope of variations to the present disclosure.

Conditional language, such as, among others, “can,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or steps. Thus, such conditional language is not generally intended to imply that features, elements and/or steps are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without user input or prompting, whether these features, elements and/or steps are included or are to be performed in any particular embodiment.

Any process descriptions, elements, or blocks in the flow diagrams described herein and/or depicted in the attached figures should be understood as potentially representing modules, segments, or portions of code which include one or more executable instructions for implementing specific logical functions or steps in the process. Alternate implementations are included within the scope of the embodiments described herein in which elements or functions may be deleted, executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those skilled in the art. It will further be appreciated that the data and/or components described above may be stored on a computer-readable medium and loaded into memory of the computing device using a drive mechanism associated with a computer-readable medium storing the computer executable components, such as a CD-ROM, DVD-ROM, or network interface; further, the component and/or data can be included in a single device or distributed in any manner. Accordingly, general purpose computing devices may be configured to implement the processes, algorithms and methodology of the present disclosure with the processing and/or execution of the various data and/or components described above.

It should be emphasized that many variations and modifications may be made to the above-described embodiments, the elements of which are to be understood as being among other acceptable examples. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the following claims. 

What is claimed is:
 1. A computer-implemented method comprising: obtaining a domain name system (DNS) query from a client computing device at a first DNS server of a content delivery network (CDN) service provider, wherein the DNS query corresponds to a requested resource and comprises a first uniform resource locator (URL), and wherein the CDN service provider is configured to provide the requested resource to the client computing device; selecting a second DNS server from one or more alternative DNS servers of the CDN service provider based, at least in part, on at least a calculated distance from each of the one or more alternative DNS servers, the second DNS server associated with a second URL, and wherein the second URL is different from the first URL; obtaining a second DNS query from the client computing device at the second DNS server, the second DNS query corresponding to the second URL; resolving the second DNS query, at the second DNS server, to identify a cache component for providing the requested resource; and transmitting information identifying the identified cache component to the client computing device, wherein the first and second URLs include information identifying a domain of the CDN service provider.
 2. The method as recited in claim 1, wherein selecting the second DNS server from the one or more alternative DNS servers based, at least in part, on at least a calculated distance from each of the one or more alternative DNS servers includes selecting the second DNS server based, at least in part, on a calculated distance from each of the one or more alternate DNS servers and a reference node in a communication network.
 3. The method as recited in claim 1, wherein selecting the second DNS server from the one or more alternative DNS servers based, at least in part, on at least a calculated distance from each of the one or more alternative DNS servers includes selecting the second DNS server based, at least in part, on a calculated distance from each of the one or more alternate DNS servers and the client computing device.
 4. The method as recited in claim 1, wherein selecting the second DNS server from the one or more alternative DNS servers based, at least in part, on at least a calculated distance from each of the one or more alternative DNS servers includes determining a calculated maximum distance as a product of a latency time associated with a selected DNS server and a speed of transmission.
 5. The method as recited in claim 1, wherein selecting the second DNS server from the one or more alternative DNS servers further includes selecting the second DNS server from the one or more alternative DNS servers based, at least in part, on performance measurement information associated with each of the one or more alternative DNS servers.
 6. The method as recited in claim 5, wherein selecting the second DNS server from the one or more alternative DNS servers based, at least in part, on performance measurement information associated with each of the one or more alternative DNS servers includes: determining performance measurement information for the one or more DNS servers; determining whether the performance measurement information exceeds a minimum performance threshold; and excluding DNS servers in which performance measurement information does not exceed the performance threshold.
 7. The method as recited in claim 6, wherein the performance measurement information corresponds to a measured latency.
 8. The method as recited in claim 1, wherein selecting the second DNS server from one or more alternative DNS servers includes: determining that the first resource identifier is associated with an alternative DNS server; and identifying the one or more alternative DNS servers that are authoritative to first DNS query.
 9. A system comprising: a first network point of presence (POP) including a domain name system (DNS) server of a content delivery network (CDN) service provider, wherein the DNS server receives a DNS query from a client computing device, wherein the DNS query corresponds to a requested resource and comprises a first uniform resource locator (URL), wherein the CDN service provider is configured to provide the requested resource to the client computing device, and wherein the DNS server in the first network POP includes a hardware component and is operative to: select a second DNS server from one or more alternative DNS servers of the CDN service provider based, at least in part, on at least a calculated distance from each of the one or more alternative DNS servers; and transmit an alternative URL corresponding to the second DNS server, wherein the alternative URL is different from the first URL; and a second network POP including a DNS server of the CDN server provider that receives a subsequent DNS query from the client computing device, wherein the subsequent DNS query corresponds to the requested resource associated with the first and alternative URLs, and wherein the DNS server in the second network POP includes a hardware component and is operative to: resolve the subsequent DNS query to identify a cache component for providing the requested resource; and transmit information identifying the identified cache component to the client computing device, wherein the first and alternative URLs include information identifying a domain of the CDN service provider.
 10. The system as recited in claim 9, wherein the alternative URL corresponds to a canonical name record identifier.
 11. The system as recited in claim 9, wherein selecting the second DNS server from the one or more alternative DNS servers based, at least in part, on at least a calculated distance from each of the one or more alternative DNS servers includes selecting the second DNS server based, at least in part, on a calculated distance from each of the one or more alternate DNS servers and a reference node in a communication network.
 12. The system as recited in claim 9, wherein selecting the second DNS server from the one or more alternative DNS servers based, at least in part, on at least a calculated distance from each of the one or more alternative DNS servers includes selecting the second DNS server based, at least in part, on a calculated distance from each of the one or more alternate DNS servers and the client computing device.
 13. The system as recited in claim 9, wherein selecting the second DNS server from the one or more alternative DNS servers based, at least in part, on at least a calculated distance from each of the one or more alternative DNS servers includes determining a calculated maximum distance as a product of a latency time associated with a selected DNS server and a speed of transmission.
 14. The system as recited in claim 9, wherein selecting the second DNS server from the one or more alternative DNS servers further includes selecting the second DNS server from the one or more alternative DNS servers based, at least in part, on performance measurement information associated with each of the one or more alternative DNS servers.
 15. The system as recited in claim 14, wherein selecting the second DNS server from the identified one or more alternative DNS servers based, at least in part, on performance measurement information associated with each of the one or more alternative DNS servers includes: determining performance measurement information for the one or more DNS servers; determining whether the performance measurement information exceeds a minimum performance threshold; and excluding DNS servers in which performance measurement information does not exceed the performance threshold.
 16. The system as recited in claim 14, wherein the performance measurement information corresponds to a measured latency.
 17. The system as recited in claim 9, wherein information identifying the identified cache component to the client computing device includes a network address of a cache component in the second network POP.
 18. The system as recited in claim 9, wherein information identifying the identified cache component to the client computing device includes a network address of a cache component in another network POP. 